The correct answers are B Benin's brass makers brought fame and wealth to its well-organized capital, and C Songhai reached its greatest size under Askia Muhammad.
Indeed, the Kingdom of Benin was located in what is now the southern part of Nigeria. Its capital was Edo (now called Benin City), a huge city surrounded by a vast system of walls and military fortifications and its artisans were famous for their bronze artifacts.
The Songhai Empire did reach it greatest size under the reign of Askia Muhammad I, Known as Askia The Great. that is 540,000 square miles at its territorial peak in 1500.
Answer A is false. The kingdom of Benin consisted of what is now southern Nigeria and the climate in that area is a tropical rainforest climate, with lots of trees and rainfall. Answer D is also false, the capital of the Songhai Empire was Gao, though Timbuktu was an important trading and commercial center.